Add utterances doc to README

Revert "base template: Fix multilingual extra //'s"

Unfortunately this fix causes a new bug with sites hosted within a
directory of a domain (eg: justintennant.me/papaya) where the menu items
would be missing a "/" inbetween the base url and the menu item slug
(eg: justintennant.me/papayablog instead of
justintennant.me/papaya/blog).

I'm not sure what a clean solution is yet to both these problems so I'm
reverting for now.

This reverts commit 9da007e.

Merge pull request #3 from cs-qyzhang/main

Add basic i18n support; add customizable social links; using relative path in img() shortcode

Center tables

README.md: Add demo site link

Add banner to index